Process and apparatus for recovery of dichlorohydrins via codistillation

ABSTRACT

A process and apparatus for recovering dichlorohydrins from a mixture comprising dichlorohydrins, one or more compounds selected from esters of dichlorohydrins, monochlorohydrins and/or esters thereof, and multihydroxylated-aliphatic hydrocarbon compounds and/or esters thereof, and optionally one or more substances comprising water, chlorinating agents, catalysts and/or esters of catalysts is disclosed. The mixture is stripped to recover dichlorohydrin(s) while distilling or fractionating the mixture to separate a lower boiling fraction comprising dichlorohydrin(s) from the mixture in one step. Advantages include more efficient recovery of dichlorohydrins for a given distillation column, less waste due to avoiding the conditions conducive to the formation of heavy byproducts, and reduced capital investment in recovery equipment.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a §371 application of PCT International Patent ApplicationNumber PCT/US2008/059976 filed Apr. 11, 2008, and claims priority fromprovisional application Ser. No. 60/923,102 filed Apr. 12, 2007, each ofwhich is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to processes and apparatus for recoveringdichlorohydrins from a mixture comprising the same such as the effluentgenerated by a process for converting multihydroxylated-aliphatichydrocarbon compound(s) and/or ester(s) thereof to chlorohydrins.

Dichlorohydrins are useful in preparing epoxides such asepichlorohydrins. Epichlorohydrin is a widely used precursor to epoxyresins. Epichlorohydrin is a monomer which is commonly used for thealkylation of para-bisphenol A. The resultant diepoxide, either as afree monomer or oligomeric diepoxide, may be advanced to high molecularweight resins which are used for example in electrical laminates, cancoatings, automotive topcoats and clearcoats.

Glycerin is considered to be a low-cost, renewable feedstock that is aco-product of the biodiesel process for making fuel. It is known thatother renewable feedstocks such as fructose, glucose and sorbitol can behydrogenolized to produce mixtures of vicinal diols and triols, such asglycerin, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycoland the like. With abundant and low cost glycerin or mixed glycols,economically attractive processes for recovering dichlorohydrins fromeffluents produced by the above processes are desired.

A process is known for the conversion of glycerol (also referred toherein as “glycerin”) to mixtures of dichloropropanols, compounds I andII, as shown in Scheme 1 below. The reaction is carried out in thepresence of anhydrous HCl and an acetic acid (HOAc) catalyst with waterremoval. Compounds I and II can then be converted to epichlorohydrin viatreatment with caustic or lime.

Various processes using the above chemistry in Scheme 1 have beenreported in the prior art. For example, epichlorohydrin can be preparedby reacting a dichloropropanol such as 2,3-dichloro-1-propanol or1,3-dichloro-2-propanol with base. Dichloropropanol, in turn, can beprepared at atmospheric pressure from glycerol, anhydrous hydrochloricacid, and an acid catalyst. A large excess of hydrogen chloride (HCl)was recommended to promote the azeotropic removal of water that isformed during the course of the reaction.

WO 2006/020234 A1 describes a process for conversion of a glycerol or anester or a mixture thereof to a chlorohydrin, comprising the step ofcontacting a multihydroxylated-aliphatic hydrocarbon compound, an esterof a multihydroxylated-aliphatic hydrocarbon, or a mixture thereof witha source of a superatmospheric partial pressure of hydrogen chloride toproduce chlorohydrins, esters of chlorohydrins, or mixtures thereof inthe presence of an organic acid catalyst. This process is also referredto herein as a “dry process”. Azeotropic removal of water in a dryprocess via a large excess of hydrogen chloride is not required toobtain high chlorohydrins yield. Separation of the product stream fromthe reaction mixture may be carried out with a suitable separationvessel such as one or more distillation columns, flash vessels,extraction columns or adsorption columns. WO 2006/020234 A1 does notdescribe a specific distillation method or a method to minimizeformation of heavy byproducts.

WO 2005/021476 A1 describes a process using atmospheric partial pressureof hydrogen chloride, acetic acid as the catalyst, and a cascade ofloops, preferably three loops, each loop consisting of a reactor and adistillation column in which water of reaction, residual hydrogenchloride and dichloropropanol are removed from the reaction effluent.This process for distillation requiring a cascade ofreactor/distillation loops is very expensive as it requires severalreactors/columns in the process. WO 2005/021476 A1 also does notdescribe specific distillation method and the method to minimizeformation of heavy byproducts. Furthermore, valuable acetic acid is lostwith the distillate, needing to add more acetic acid to make up for thecatalyst loss in distillation.

EP 1 752 435 A1 discloses another process for producing a chlorohydrinby reaction between a multihydroxylated aliphatic hydrocarbon and/or anester thereof and aqueous hydrogen chloride to produce chlorohydrins,esters of chlorohydrins, or mixtures thereof under atmospheric conditionin which a purge from the reactor bottom is fed to a stripper in whichpartial stripping of most of unreacted hydrogen chloride, the water fromthe aqueous hydrogen chloride reactant and water that is formed duringthe course of the reaction (also referred to herein as “water ofreaction”), from the reaction mixture is carried out and a distillationor stripping column is fed with the liquid phase from the stripper. Thegas phase from the stripper, which contains most of the unreactedhydrogen chloride, the excess water from the aqueous hydrogen chloridereactant and the reaction by-product water from the reaction mixture, isconducted to a distillation column fed by the vapor produced by thereactor or is recycled directly to the reactor. The main fraction ofdichloropropanol is collected from the top of the distillation orstripping column. The column residue is recycled to reactor. Thisprocess (also referred to herein as a “wet process”), not only addswater via the aqueous hydrogen chloride reactant into the process, butalso produces water of reaction in the process. The removal of largeexcess of water in the wet process via stripper is less energy efficientand unnecessary for the dry process. A better utilization of thestripper can be done in the recovery of dichloropropanol. EP 1 752 435A1 also does not describe a specific distillation method to minimizeformation of heavy byproducts.

CN 101007751A describes another process that combines wet and dryprocesses with two reactor in series, in which tubular reactor is usedas the first reactor and foaming-tank reactor is used as the secondreactor. Aqueous hydrogen chloride, glycerin, carboxylic acid catalystare mixed and fed to the first reactor and gaseous hydrogen chloride isfed to the second reactor. Inert impurities are added to the gaseoushydrogen chloride feed in order to improve the efficiency of strippingwater from the reaction mixture in the foaming-tank reactor. Theazeotropic composition of generated water, dichloropropanol and hydrogenchloride and part of the catalyst are evaporated from the top offoaming-tank reactor. The liquid bottom product of the foaming-tankreactor enters to a rectifying tower for separation. Thedichloropropanol product is obtained from the rectifying towerdistillates and the tower bottom residue is recycled to the foaming-tankreactor. This process shows lower hydrogen chloride conversion than thatof the dry process, generates excess water where azeotropic removal ofwater is required, which implies larger process equipment than that ofthe dry process. CN 101007751A also does not describe specificdistillation method to minimize formation of heavy byproducts.

Opportunities remain to further improve the recovery of dichlorohydrinsin a form that can be used in subsequent conversions, such as theconversion to epichlorohydrin.

SUMMARY OF THE INVENTION

One aspect of the present invention is a process for recoveringdichlorohydrin(s) from a mixture comprising dichlorohydrin(s), one ormore compounds selected from ester(s) of chlorohydrin(s),monochlorohydrin(s), and/or multihydroxylated-aliphatic hydrocarboncompound(s) and/or ester(s) thereof, and optionally one or moresubstances comprising water, chlorinating agent(s), catalyst(s),ester(s) of catalyst(s), and/or heavy byproduct(s), wherein the processcomprises:

-   -   (a) providing a mixture comprising dichlorohydrin(s), one or        more compounds selected from ester(s) of chlorohydrin(s),        monochlorohydrin(s), and/or multihydroxylated-aliphatic        hydrocarbon compound(s) and/or ester(s) thereof, and optionally        one or more substances comprising water, chlorinating agent(s),        catalyst(s), ester(s) of catalyst(s), and heavy byproduct(s);    -   (b) distilling or fractionating the mixture of step (a) in one        or more unit operations to separate a lower boiling fraction        comprising dichlorohydrin(s) and other lower boiling components        present in the mixture from the mixture of step (a) to form a        higher boiling fraction comprising the residue of the        distillation or fractionation;    -   (c) introducing at least one stripping agent into contact with        the higher boiling fraction produced by step (b) for stripping        dichlorohydrin(s) from the higher boiling fraction with the at        least one stripping agent to produce additional lower boiling        fraction enriched with dichlorohydrin(s) and the at least one        stripping agent; and    -   (d) recovering the lower boiling fraction produced in steps (b)        and (c) during step (b).

Another aspect of the present invention is a method for producingdichlorohydrin(s), wherein the mixture provided in step (a) is producedor derived from hydrochlorination of monochlorohydrin(s) and/or ester(s)thereof and/or multihydroxylated-aliphatic hydrocarbon compound(s)and/or ester(s) thereof.

Yet another aspect of the present invention is an apparatus suitable forproducing dichlorohydrin(s) from multihydroxylated-aliphatic hydrocarboncompound(s) and/or ester(s) thereof comprising:

-   -   (1) at least one reactor;    -   (2) at least one separation device comprising at least one        liquid-vapor contacting device having a bottom end and a top end        for applying a decreasing temperature gradient from the bottom        end to the top end to substances within the liquid-vapor        contacting device; and    -   (3) at least one port proximal to the bottom end of the at least        one liquid-vapor contacting device of the separation device (2)        for introducing stripping agent into the bottom end of the at        least one liquid-vapor contacting device of the separation        device (2),

wherein

-   -   the at least one reactor (1) is connected directly or indirectly        to the at least one separation device (2) for conducting a        reactor effluent stream from the at least one reactor (1) to the        at least one liquid-vapor contacting device of the at least one        separation device (2) for distillation and/or fractionation, and    -   the at least one port (3) is connected to at least one source of        stripping agent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a process diagram illustrating one embodiment of the processof the present invention.

DETAILED DESCRIPTION OF THE INVENTION Definitions

As used herein, the term “multihydroxylated-aliphatic hydrocarboncompound” (abbreviated hereafter as “MAHC”) refers to a compound thatcontains at least two hydroxyl groups covalently bonded to two separatevicinal carbon atoms and no ether linking groups. They contain at leasttwo sp3 hybridized carbons each bearing an OH group. The MAHCs includeany vicinal-diol (1,2-diol) or triol (1,2,3-triol) containinghydrocarbon including higher orders of contiguous or vicinal repeatunits. The definition of MAHC also includes for example one or more1,3-1,4-, 1,5- and 1,6-diol functional groups as well. Geminal-diols,for example, are precluded from this class of MAHCs.

The MAHCs contain at least 2, preferably at least 3, up to about 60,preferably up to 20, more preferably up to 10, even more preferably upto 4, and yet more preferably up to 3, carbon atoms and can contain, inaddition to aliphatic hydrocarbon, aromatic moieties or heteroatomsincluding for example halide, sulfur, phosphorus, nitrogen, oxygen,silicon, and boron heteroatoms; and mixtures thereof. The MAHCs may alsobe a polymer such as polyvinyl alcohol.

The terms “glycerin”, “glycerol” and “glycerine”, and esters thereof,may be used as synonyms for the compound 1,2,3-trihydroxypropane, andesters thereof.

As used herein, the term “chlorohydrin” means a compound containing atleast one hydroxyl group and at least one chlorine atom covalentlybonded to two separate vicinal aliphatic carbon atoms and no etherlinking groups. Chlorohydrins are obtainable by replacing one or morehydroxyl groups of MAHCs with covalently bonded chlorine atoms viahydrochlorination. The chlorohydrins contain at least 2, and preferablyat least 3, up to about 60, preferably up to 20, more preferably up to10, even more preferably up to 4, and yet more preferably up to 3,carbon atoms and, in addition to aliphatic hydrocarbon, can containaromatic moieties or heteroatoms including for example halide, sulfur,phosphorus, nitrogen, oxygen, silicon, and boron heteroatoms, andmixtures thereof. A chlorohydrin that contains at least two hydroxylgroups is also a MAHC.

As used herein, the term “monochlorohydrin” means chlorohydrin havingone chlorine atom and at least two hydroxyl groups, wherein the chlorineatom and at least one hydroxyl group are covalently bonded to twoseparate vicinal aliphatic carbon atoms (referred to hereafter by theabbreviation “MCH”). MCH produced by hydrochlorination of glycerin orglycerin esters includes, for example, 3-chloro-1,2-propanediol and2-chloro-1,3-propanediol.

As used herein, the term “dichlorohydrin” means chlorohydrin having twochlorine atoms and at least one hydroxyl group, wherein at least onechlorine atom and at least one hydroxyl group are covalently bonded totwo separate vicinal aliphatic carbon atoms (referred to hereafter bythe abbreviation “DCH”). Dichlorohydrins produced by hydrochlorinationof glycerin or glycerin esters include 1,3-dichloro-2-propanol and2,3-dichloro-1-propanol.

As used herein, the expression “under hydrochlorination conditions”means conditions capable of converting at least 1 wt. %, preferably atleast 5 wt. %, more preferably at least 10 wt. % of MAHCs, MCHs, andesters of MAHCs and MCHs present in a mixture and/or feed stream intoDCH(s) and/or ester(s) thereof.

As used herein, the term “byproduct(s)” means compound(s) that is/arenot chlorohydrin(s) and/or ester(s) thereof and/or chlorinating agent(s)and that do not form chlorohydrin(s) and/or ester(s) thereof under thehydrochlorinating conditions selected according to the presentinvention.

The expression “heavy byproduct(s)” refer to oligomers of mixture (a)components, such as oligomers of MAHCs and/or esters thereof andoligomers of chlorohydrins and/or esters thereof, and derivatives ofsuch oligomers, such as esters thereof, chlorinated oligomers, and/orchlorinated esters thereof, having a number average molecular weightequal to or greater than the number average molecular weight of theoligomer, such as chlorinated oligomers. The terms chlorohydrin(s),MCH(s) and DCH(s), and ester(s) thereof, are not intended to includeheavy byproducts.

The term “epoxide” means a compound containing at least one oxygenbridge on a carbon-carbon bond. Generally, the carbon atoms of thecarbon-carbon bond are contiguous and the compound can include otheratoms than carbon and oxygen atoms, like hydrogen and halogens, forexample. Preferred epoxides are ethylene oxide, propylene oxide,glycidol and epichlorohydrin.

As used herein, the expression, “liquid phase” refers to a continuousintermediate phase between gas phase and a solid phase that mayoptionally comprise a minor amount of gas and/or solid discretephase(s). The liquid phase may comprise one or more immiscible liquidphases and may contain one or more dissolved solids, such as one or moreacids, bases, or salts.

As used herein, the expression “vapor phase” refers to a continuousgaseous phase that may optionally comprise a minor amount of liquidand/or solid discrete phase(s) (e.g., aerosol). The vapor phase may be asingle gas or a mixture, such as a mixture of two or more gases, two ormore liquid discrete phases, and/or two or more solid discrete phases.

The expression “lower boiling fraction” refers to a fraction derivedfrom the mixture provided in step (a) in which more than half the totalquantity of components of the lower boiling fraction are components ofthe mixture, or derived from the mixture, that are more volatile underthe conditions of the unit operation than the components of the higherboiling fraction in the same unit operation derived from the samemixture provided in step (a).

The expression “higher boiling fraction” refers to a fraction derivedfrom the mixture provided in step (a) in which more than half the totalquantity of components of the higher boiling fraction are components ofthe mixture, or derived from the mixture, that are less volatile thanthe components of the lower boiling fraction in the same unit operationderived from the same mixture provided in step (a).

As used herein, the expression “liquid-vapor contacting device” refersto devices that serve to provide the contacting and development of atleast one interfacial surface between liquid and vapor in the device.Examples of liquid-vapor contacting devices include plate column, packedcolumn, wetted-wall (falling film) column, spray chamber, heat exchangeror any combination thereof. Examples of devices comprising plate columnsand packed columns include distillation columns, fractionation columns,and stripping columns.

As used herein, the term “condenser” means a non-adiabatic system forremoving heat from a process fluid via a secondary fluid physicallyseparated from the process fluid. The process fluid and the secondaryfluid may each be a vapor, a liquid, or a combination of liquid andvapor. A condenser is generally associated with a section of adistillation or fractionation liquid-vapor contacting device. It may bea unit operation external to a distillation column or it may be a unitoperation internal to a distillation column. The physical separation maybe in the form of tubes and the condensation may be carried out on theinside or outside of the tubes. The condenser may take the form ofcooling elements on the decks of distillation column fractionating traysor as cooling elements between distillation column packing beds.

Mixture (a):

Mixture (a) may be obtained directly or indirectly from anyhydrochlorination process well-known in the art. For example, GermanPatent No. 197308 teaches a process for preparing a chlorohydrin by thecatalytic hydrochlorination of glycerin by means of anhydrous hydrogenchloride. WO 2005/021476 discloses a continuous process for preparingthe dichloropropanols by hydrochlorination of glycerin and/ormonochloropropanediols with gaseous hydrogen chloride with catalysis ofa carboxylic acid. WO 2006/020234 A1 describes a process for conversionof a glycerol or an ester or a mixture thereof to a chlorohydrin,comprising the step of contacting a MAHC, an ester of a MAHC, or amixture thereof with a source of a superatmospheric partial pressure ofhydrogen chloride to produce a chlorohydrin, an ester of a chlorohydrin,or a mixture thereof in the presence of an organic acid catalyst withoutsubstantially removing water. The above references are herebyincorporated herein by reference with respect to the above-describeddisclosures.

In an exemplifying hydrochlorination process, MAHC and ahydrochlorination catalyst are charged to the hydrochlorination reactor.Then a chlorinating agent such as hydrogen chloride is added to thereactor. The reactor pressure is adjusted to the desired pressure andthe reactor contents are heated to the desired temperature for thedesired length of time. After completion of the hydrochlorinationreaction or while carrying out the hydrochlorination reaction, thereactor contents as a reaction effluent stream is discharged from thereactor and fed directly, or indirectly via another reactor or otherintervening step, to a separation system comprising a DCH recoverysystem according to the present invention and optionally including otherseparation systems or equipment, such as a flash vessel and/or reboiler.

The hydrochlorination reaction above may be carried out in one or morehydrochlorination reactor vessels such as a single or multiplecontinuous stirred tank reactors (referred to hereafter by theabbreviation “CSTR”), single or multiple tubular reactor(s), plug flowreactors (referred to hereafter by the abbreviation “PFR”), orcombinations thereof. The hydrochlorination reactor can be, for example,one reactor or multiple reactors connected with each other in series orin parallel including, for example, one or more CSTRs, one or moretubular reactors, one or more PFRs, one or more bubble column reactors,and combinations thereof.

In a preferred embodiment, part or all of the hydrochlorination effluentstream is a feed stream from a PFR. A PFR is a type of reactor that hasa high length/diameter (L/D) ratio and has a composition profile alongthe length of the reactor. The concentration of the reactants being fedinto the PFR decreases from inlet to the outlet along the flow path ofthe PFR and the concentration of DCHs increases from inlet to the outletalong the flow path of the PFR. In the case of hydrochlorination ofglycerol, the concentration of HCl and glycerol decreases from inlet ofthe PFR to outlet of the PFR while the total concentration of1,3-dichloro-2-propanol and 2,3-dichloro-1-propanol increases from inletof the PFR to the outlet of the PFR.

The equipment useful for conducting the hydrochlorination reaction maybe any well-known equipment in the art and should be capable ofcontaining the reaction mixture at the conditions of thehydrochlorination. Suitable equipment may be fabricated of materialswhich are resistant to corrosion by the process components, and mayinclude for example, metals such as tantalum, suitable metallic alloys(particularly nickel-molybdenum alloys such as Hastalloy C©), orglass-lined equipment, for example.

In addition to DCH(s), one or more of the unreacted MAHC(s) and/orchlorination agent(s), reaction intermediates such as MCH(s), MCHester(s), and/or DCH ester(s), catalyst(s), ester(s) of catalyst(s),water, and/or heavy byproduct(s) may present in mixture (a). A recycleprocess is preferred in which one or more of the unreacted MAHC(s),ester(s) of MAHC(s) and/or chlorination agent(s), reaction intermediatessuch as MCH(s), MCH ester(s), DCH ester(s), and other substances such ascatalyst(s), ester(s) of catalyst(s), and water are preferably recycledto a prior step in the process, such as to at least onehydrochlorination reactor for further hydrochlorination. In particular,a liquid higher boiling fraction comprising a residue of the distillingor fractionating step containing one or more of MAHC(s), MCH(s),catalyst(s), and/or ester(s) of one or more MAHC(s), MCH(s), DCH(s)and/or catalyst(s), and preferably a combination of two or more thereof,is recycled to the hydrochlorination step, such as by recycling thehigher boiling fraction to one or more reactor(s), Such recycleprocess(es) is preferably continuous. In this manner, raw materialefficiencies are maximized and/or catalysts are reused.

When catalysts are reused in such a process scheme, it may be desirableto employ the catalysts in a higher concentration than they are employedin a single-pass process. This may result in faster reactions, orsmaller process equipment, which results in lower capital costs for theequipment employed.

In a continuous recycle process, undesirable impurities and/or reactionbyproducts may build up in the process. Thus, it is desirable to providea means for removing such impurities from the process, such as via oneor more purge outlets, for example, or by a separation step.Furthermore, a purged stream may be further treated to recover a usefulportion of the purged stream.

The chlorinating agent that may optionally be present in the mixturetreated according to the present invention is preferably hydrogenchloride or hydrogen chloride source, and may be a gas, a liquid or in asolution, or a mixture thereof. The hydrogen chloride is preferablyintroduced in the gaseous state and, when the hydrochlorination reactionmixture is in the liquid phase, at least some of the hydrogen chloridegas is preferably dissolved in the liquid reaction mixture. The hydrogenchloride may, however, be diluted in a solvent, such as an alcohol (forexample methanol), or in a carrier gas such as nitrogen, if desired.

It is preferred that the hydrochlorination step of the present inventionbe carried out under superatmospheric pressure conditions.“Superatmospheric pressure” herein means that the hydrogen chloride(HCl) partial pressure is above atmospheric pressure, i.e. 15 psia (103kPa) or greater. Generally, the hydrogen chloride partial pressureemployed in the hydrochlorination process is at least about 15 psia (103kPa) or greater. Preferably, the hydrogen chloride partial pressureemployed in the hydrochlorination process is not less than about 25 psia(172 kPa), more preferably not less than about 35 psia (241 kPa), andmost preferably not less than about 55 psia (379 kPa); and preferablynot greater than about 1000 psia (6.9 MPa), more preferably not greaterthan about 600 psia (4.1 MPa), and most preferably not greater thanabout 150 psia (1.0 MPa).

It is also preferred to conduct the hydrochlorination step at atemperature sufficient for hydrochlorination that is also below theboiling point of the chlorohydrin(s) in the reaction mixture having thelowest boiling point for a given pressure condition during thehydrochlorination step in order to keep the chlorohydrin(s) produced andconverted during hydrochlorination in the liquid phase of the reactionmixture for recovery in steps (b) and (c). The upper limit of thispreferred temperature range may be adjusted by adjusting the pressurecondition. A higher pressure during hydrochlorination may be selected toincrease the boiling point temperature of the chlorohydrin(s) in thereaction mixture, so that the preferred temperature range for keepingDCH(s) in the liquid phase may be increased by increasing the pressurecondition.

Preferably, less than 50, more preferably less than 10, even morepreferably less than 5, and yet more preferably less than 1, percent ofthe DCH present in the hydrochlorination effluent is removed from thehydrochlorination effluent prior to step (b).

The hydrochlorination effluent comprises one or more DCHs, one or morecompounds comprising ester(s) of DCH(s), MCH(s) and/or ester(s) thereof,and MAHC(s) and/or ester(s) thereof, and optionally one or moresubstances comprising water, chlorination agent(s), catalyst(s) and/orester(s) of catalyst(s). Additional optional components may also bepresent in the effluent depending on the starting materials, reactionconditions, and any process steps intervening between thehydrochlorination reaction and recovery of DCH according to the presentinvention. The hydrochlorination effluent is preferably in the liquidphase as the hydrochlorination effluent is withdrawn from thehydrochlorination step and/or reactor and the mixture provided in step(a) comprises at least part of the liquid phase effluent of thehydrochlorination step.

In a preferred embodiment, at least one MAHC and/or ester thereof ispresent in the mixture provided in step (a). When MAHC(s) and/orester(s) thereof is/are present in the mixture provided in step (a), thesame MAHC(s) and/or ester(s) thereof may also be present in thehigh-boiling fraction of step (b).

MAHCs found in the effluent treated according the present invention mayinclude for example 1,2-ethanediol; 1,2-propanediol; 1,3-propanediol;3-chloro-1,2-propanediol; 2-chloro-1,3-propanediol; 1,4-butanediol;1,5-pentanediol; cyclohexanediols; 1,2-butanediol;1,2-cyclohexanedimethanol; 1,2,3-propanetriol (also known as, and usedherein interchangeable as, “glycerin”, “glycerine”, or “glycerol”); andmixtures thereof. Preferably, the MAHCs in the effluents treatedaccording to the present invention include for example 1,2-ethanediol;1,2-propanediol; 1,3-propanediol; and 1,2,3-propanetriol; with1,2,3-propanetriol being most preferred.

Examples of esters of MAHCs found in the effluents treated according tothe present invention include for example ethylene glycol monoacetate,propanediol monoacetates, glycerin monoacetates, glycerin monostearates,glycerin diacetates, and mixtures thereof. In one embodiment, suchesters can be made from mixtures of MAHC with exhaustively esterifiedMAHC, for example mixtures of glycerol triacetate and glycerol.

In the same or another preferred embodiment, at least one MCH and/orester thereof is present in the mixture provided in step (a). WhenMCH(s) and/or ester(s) thereof is/are present in the mixture provided instep (a), the same MCH(s) and/or ester(s) thereof may also be present inthe high-boiling fraction of step (b).

The MCHs generally correspond to the hydrochlorinated MAHCs in which oneof a pair of hydroxyl groups covalently bonded to two separate vicinalcarbon atoms is replaced by a covalently bonded chlorine atom. Theester(s) of MCH may be the result of hydrochlorination of MAHC ester(s)or reaction with an acid catalyst, for example.

The DCHs generally correspond to the hydrochlorinated MAHCs in which twohydroxyl groups covalently bonded to two separate carbon atoms, at leastone of which is vicinal to a third carbon atom having a hydroxyl group,are each replaced by a covalently bonded chlorine atom. The ester(s) ofDCH may be the result of hydrochlorination of MAHC ester(s), MCHester(s) or reaction(s) with acid catalyst(s), for example.

In an embodiment of the present invention where MAHC(s) is/are thestarting material fed to the process, as opposed to ester(s) of MAHC(s)or a mixture of MAHC(s) and ester(s) thereof as a starting material, itis generally preferred that the formation of chlorohydrin be promoted bythe presence of one or more catalyst(s) and/or ester(s) thereof.Catalyst(s) and/or ester(s) thereof may also be present where ester(s)of MAHC(s), or a mixture of MAHC(s) and ester(s) thereof, is a startingmaterial to further accelerate the hydrochlorination reaction.

Carboxylic acids, RCOOH, catalyze the hydrochlorination of MAHCs tochlorohydrins. The specific carboxylic acid catalyst chosen may be basedupon a number of factors including for example, its efficacy as acatalyst, its cost, its stability to reaction conditions, and itsphysical properties. The particular process, and process scheme in whichthe catalyst is to be employed may also be a factor in selecting theparticular catalyst. The “R” groups of the carboxylic acid may beindependently chosen from hydrogen or hydrocarbyl groups, includingalkyl, aryl, aralkyl, and alkaryl. The hydrocarbyl groups may be linear,branched or cyclic, and may be substituted or un-substituted.Permissible substituents include any functional group that does notdetrimentally interfere with the performance of the catalyst, and mayinclude heteroatoms. Non-limiting examples of permissible functionalgroups include chloride, bromide, iodide, hydroxyl, phenol, ether,amide, primary amine, secondary amine, tertiary amine, quaternaryammonium, sulfonate, sulfonic acid, phosphonate, and phosphonic acid.

The carboxylic acids useful as hydrochlorination catalysts may bemonobasic such as acetic acid, formic acid, propionic acid, butyricacid, isobutyric acid, hexanoic acid, 4-methylvaleric acid, heptanoicacid, oleic acid, or stearic acid; or polybasic such as succinic acid,adipic acid, or terephthalic acid. Examples of aralkyl carboxylic acidsinclude phenylacetic acid and 4-aminophenylacetic acid. Examples ofsubstituted carboxylic acids include 4-aminobutyric acid,4-dimethylaminobutyric acid, 6-aminocaproic acid, 6-hydroxyhexanoicacid, 6-chlorohexanoic acid, 6-aminohexanoic acid, 4-aminophenylaceticacid, 4-hydroxyphenylacetic acid, lactic acid, glycolic acid,4-dimethylaminobutyric acid, and 4-trimethylammoniumbutyric acid.Additionally, materials that can be converted into carboxylic acidsunder reaction conditions, including for example carboxylic acidhalides, such as acetyl chloride, 6-chlorohexanoyl chloride,6-hydroxyhexanoyl chloride, 6-hydroxyhexanoic acid, and4-trimethylammonium butyric acid chloride; carboxylic acid anhydridessuch as acetic anhydride and maleic anhydride; carboxylic acid esterssuch as methyl acetate, methyl propionate, methyl pivalate, methylbutyrate, ethylene glycol monoacetate, ethylene glycol diacetate,propanediol monoacetates, propanediol diacetates, glycerin monoacetates,glycerin diacetates, glycerin triacetate, and glycerin esters of acarboxylic acid (including glycerin mono-, di-, and tri-esters); MAHCacetates such as glycerol 1,2-diacetate; carboxylic acid amides such asε-caprolactam and γ-butyrolactam; and carboxylic acid lactones such asγ-butyrolactone, δ-valerolactone and ε-caprolactone may also be employedin the present invention. Zinc acetate is an example of a metal organiccompound. Mixtures of the foregoing catalysts and catalyst precursorsmay also be used.

When a catalyst is used in the superatmospheric pressure process, thecatalyst may be for example a carboxylic acid; an anhydride; an acidchloride; an ester; a lactone; a lactam; an amide; a metal organiccompound such as sodium acetate; or a combination thereof. Any compoundthat is convertible to a carboxylic acid or a functionalized carboxylicacid under hydrochlorination reaction conditions may also be used. Apreferred carboxylic acid for the superatmospheric pressure process isan acid with a functional group consisting of a halogen, an amine, analcohol, an alkylated amine, a sulfhydryl, an aryl group or an alkylgroup, or combinations thereof, wherein this moiety does not stericallyhinder the carboxylic acid group.

Certain catalysts may also be advantageously employed atsuperatmospheric, atmospheric or sub-atmospheric pressure, andparticularly in circumstances where water is continuously orperiodically removed from the reaction mixture to drive conversion todesirably higher levels as may be the case when recovering DCH(s)according to the claimed invention. For example, the hydrochlorinationof MAHC(s) reaction can be practiced by introducing hydrogen chloridegas into contact with a mixture of MAHC(s) and catalyst(s), such as bysparging the hydrogen chloride gas through a liquid phase reactionmixture. In such a process, the use of less volatile catalysts, such as6-hydroxyhexanoic acid, 4-aminobutyric acid; dimethyl 4-aminobutyricacid; 6-chlorohexanoic acid; caprolactone; carboxylic acid amides suchas ε-caprolactam and γ-butyrolactam; carboxylic acid lactones such asγ-butyrolactone, δ-valerolactone and ε-caprolactone; caprolactam;4-hydroxyphenyl acetic acid; 6-amino-caproic acid; 4-aminophenylaceticacid; lactic acid; glycolic acid; 4-dimethylamino-butyric acid;4-trimethylammoniumbutyric acid; and combination thereof; and the likemay be preferred. It is most desirable to employ a catalyst, under theseatmospheric or subatmospheric conditions, that is less volatile than theDCH(s) produced and recovered.

Preferred catalysts used in the present invention include carboxylicacids, esters of carboxylic acids, and combinations thereof,particularly esters and acids having a boiling point higher than that ofthe desired highest boiling DCH that is formed in the reaction mixture(i.e., the catalyst(s) is/are preferably less volatile than the DCH(s)in the mixture), so that the DCH(s) can be removed without removing thecatalyst. Catalysts which meet this definition and are useful in thepresent invention include for example, polyacrylic acid, glycerin estersof carboxylic acids (including glycerin mono-, di-, and tri-esters),polyethylene grafted with acrylic acid, divinylbenzene/methacrylic acidcopolymer, 6-chlorohexanoic acid, 4-chlorobutanoic acid, caprolactone,heptanoic acid, 4-hydroxyphenylacetic acid, 4-aminophenylacetic acid,6-hydroxyhexanoic acid, 4-aminobutyric acid, 4-dimethylaminobutyricacid, 4-trimethyl-ammoniumbutyric acid chloride, stearic acid,5-chlorovaleric acid, 6-hydroxyhexanoic acid, 4-aminophenylacetic acid,and mixtures thereof. Carboxylic acids that are sterically unencumberedaround the carboxylic acid group are generally preferred.

Furthermore, the catalyst(s) is/are preferably miscible with the MAHC(s)employed. For this reason, the catalyst(s) may contain polar heteroatomsubstituents such as hydroxyl, amino or substituted amino, or halidegroups, which render the catalyst miscible with the MAHC(s) in thereaction mixture, such as glycerol.

One embodiment of the catalyst that may be present is generallyrepresented by Formula (a) shown below wherein the functional group “R′”includes a functional group comprising an amine, an alcohol, a halogen,a sulfhydryl, an ether; or an alkyl, an aryl or alkaryl group of from 1to about 20 carbon atoms containing said functional group; or acombination thereof; and wherein the functional group “R” may include ahydrogen, an alkali, an alkali earth or a transition metal or ahydrocarbon functional group.

Where the catalyst is recycled and used repeatedly, such recycledcatalysts may be present in an amount from about 0.1 mole %, preferablyfrom about 1 mole %, more preferably from about 5 mole %, up to about99.9 mole %, preferably up to 70 mol %, and more preferably up to 50mole %, based on the amount in moles of MAHC present. Higher catalystsconcentrations may be desirably employed to reduce the reaction time andminimize the size of process equipment.

In a preferred embodiment, the mixture (a) comprises water, such as thewater produced as a byproduct of the hydrochlorination reaction, waterpresent in the starting materials for the hydrochlorination reaction,and/or water introduced as the stripping agent. The mixture (a) maycontain at least 1, more preferably at least 5, weight-percent water upto 90, more preferably up to 50, weight-percent water.

The mixture of step (a) may be a combination of liquid phase and vaporphase. The mixture of step (a) is preferably provided to the separationstep as a liquid phase as opposed to a gaseous or vapor phase.

In one embodiment, the mixture of step (a) is provided to step (b) byseparating a hydrochlorination reaction effluent stream into avapor-phase effluent stream and a liquid-phase effluent stream prior tostep (b) and introducing the liquid-phase effluent stream or both thevapor-phase effluent stream and the liquid-phase effluent stream,separately or combined, into step (b). The separation of the reactioneffluent stream may be carried out in, for example, a flash vesselseparate from or integral with step (b).

Recovery of DCH from the Mixture (a):

Recovery of DCH according to the present invention takes place in step(b). The mixture (a) is distilled and/or fractionated to separate alower boiling fraction comprising dichlorohydrin(s) from the mixture ofstep (a) to form a higher boiling fraction comprising the residue of thedistillation or fractionation and the residue of the higher boilingfraction is stripped by introducing at least one stripping agent intocontact with the higher boiling fraction produced by step (b) forstripping dichlorohydrin(s) from the higher boiling fraction with the atleast one stripping agent to produce a lower boiling fraction enrichedwith DCH(s) and the at least one stripping agent. DCH(s), and preferablywater, may be recovered from the lower boiling fraction of step (b).

One or more stripping agents are introduced into the higher boilingfraction of step (b) while the same higher boiling fraction is distilledor fractionated according to step (b) for contact with the higherboiling fraction undergoing distillation or fractionation and strippingDCH(s) from the higher boiling fraction.

In step (b), a stripping agent is introduced into the higher boilingfraction produced by step (b). Preferred stripping agents include steam,nitrogen, methane and carbon dioxide, and mixtures thereof.

The stripping agent is preferably an azeotroping agent for the DCH(s) inthe high boiling fraction produced in step (b). The stripping agent mayalso be a stripping agent and/or an azeotroping agent for thechlorinating agent(s) and/or for any volatile catalyst(s) present. Suchstripping agents include steam. Superheated steam is more preferred.

The stripping agent is preferably introduced into the higher boilingfraction at a temperature equal to or greater than the temperature ofthe higher boiling fraction during step (b) and is preferably introducedat a temperature equal to or greater than the boiling point of the DCHand water azeotrope at the pressure condition of step (b). The strippingagent is preferably introduced into the higher boiling fraction at atemperature that is greater, such as at least 10° C., or 20° C., or 30°C. greater, than the temperature of the higher boiling fraction tocompensate for heat loss during step (b) and thereby maintain the highboiling fraction at the desired elevated temperature.

Since the distillation residue is stripped in step (b), step (b) may beconducted under milder separation conditions than those required tooptimize DCH recovery in the absence of stripping. DCH(s), andpreferably water, may be recovered from the lower boiling fraction ofstep (b). The temperature and pressure for step (b) are preferablyadjusted to recover at least 10, more preferably at least 25, and yetmore preferably at least 50, and up to 90, more preferably up to 95, yetmore preferably up to 99, percent of the total amount of DCH in themixture provided in step (a) via the lower boiling fraction produced instep (b).

Milder separation conditions may include reducing the temperature of thedistillation bottoms to reduce energy consumption and reduce the rate ofheavy byproduct formation during step (b). Safety and efficiency areimproved when the distillation column is operated at lower bottomtemperature.

Distillation or fractionation step (b) is preferably carried out at atemperature measured in the distillation bottoms of at least 25° C.,more preferably at least 50° C., yet more preferably at least 80° C.,even more preferably at least 100° C., and yet even more preferably atleast 110° C., up to 200° C., more preferably up to 160° C., yet morepreferably up to 140° C., even more preferably up to 139° C., yet evenmore preferably up to 135° C., yet even more preferably up to 132° C.,yet even more preferably up to 125° C., and yet even more preferably upto 120° C.

Milder separation conditions may also include operation of step (b)under pressure conditions higher than those used in conventionalprocesses for separating DCH(s) from reactor effluents. The higherpressure condition process allows for energy savings and a widerselection of vacuum devices. A more economical steam-jet ejector orvacuum pump can be used, which reduces fixed capital and operatingcosts. Operational reliability is also improved through the use ofsteam-jet ejectors, because steam-jet ejectors do not have moving parts,while low pressure, high vacuum operation generally requires the use ofrotary oil-sealed vacuum pumps or multiple stages of steam-jet ejectors.Also higher distillation column pressure operation reduces column size,thereby reducing the capital investment to be amortized.

The distillation or fractionation step (b) is preferably carried out ata pressure of at least 0.1 kPa, more preferably at least 1 kPa, evenmore preferably at least 3 kPa, yet more preferably at least 6 kPa, andeven more preferably at least 10 kPa, up to 1 MPa, more preferably up to0.12 MPa, yet more preferably up to 0.05 MPa, and even more preferablyup to 0.02 MPa.

The percent DCH(s) recovered from the mixture introduced into step (b)generally depends on the combination of temperature and pressureconditions selected. To obtain a given DCH recovery in step (b), areduction in temperature generally requires a reduction in operatingpressure and an increase in operating pressure, conversely, generallyrequires an increase in operating temperature. The specific temperatureand pressure conditions selected will depend on the extent to whichrealization of the respective benefits relating to low temperature andhigher pressure operation is desired.

Step (b) is preferably carried out under conditions such that the amountof heavy byproducts in the high boiling fraction of step (b) does notexceed 110 percent, more preferably not more than 108 percent, even morepreferably not more than 105 percent, and even more preferably not morethan 102 percent, of the amount of heavy byproducts in the mixtureprovided in step (a).

The conditions during step (b) are preferably adjusted to produce ahigher boiling fraction containing less than 50, more preferably lessthan 20, even more preferably less than 10, and yet even more preferablyless than 5, percent of the chlorinating agent(s) present in the mixtureprovided in step (a). One or more conditions of step (b), such as thetemperature and pressure, may be adjusted to remove chlorinatingagent(s) from the mixture (a) provided to step (b). The stripping agentfor DCH(s) may also function as a stripping agent for the chlorinatingagent(s).

When the chlorinating agent is hydrogen chloride for example, thehydrogen chloride may be removed from the mixture (a) during step (b) bymaintaining a pressure during step (b) that is below the pressurerequired to maintain dissolution of the hydrogen chloride present in themixture provided in step (a), maintaining a temperature during step (b)that is greater than the temperature required to maintain dissolution ofthe hydrogen chloride present in the mixture provided in step (a),and/or adjusting the rate at which a stripping agent such as steam isintroduced to strip hydrogen chloride from the mixture (a).

In a preferred embodiment, the mixture provided in step (a) is passedthrough a pressure letdown step for degassing the mixture prior todistilling and/or fractionating the mixture. When there are flowfluctuations or surges upstream from the distillation and/orfractionation step, the pressure letdown step and/or a surge vessel mayalso be used to help regulate the flow of the mixture into thedistillation and/or fractionation step.

Step (b) is preferably carried out in a distillation column, such as afractional distillation column. Examples of suitable distillationcolumns include a plate or tray columns, bubble cap columns and packedcolumns.

In one embodiment, additional MAHC(s) and/or ester(s) thereof may beintroduced into step (b) for reactive distillation/fractionation. Theadditional MAHC(s) and/or ester(s) thereof may react with thechlorination agent to produce additional MCH(s) and/or ester(s) thereof.Additional MAHC(s) may also react with ester(s) of DCH(s) and MCH(s) toconvert them to non-ester(s) to facilitate recovery of DCH(s). Theadditional MAHC(s) and/or ester(s) thereof is/are preferably introducedas a liquid phase into a reflux to provide additional liquid phase forreflux.

In a preferred embodiment, step (b) comprises:

-   -   (b1) vaporizing an azeotropic mixture of DCH(s) and water from        the mixture of step (a) to separate a lower boiling fraction        comprising at least DCH(s) and water from the mixture of        step (a) and    -   (b2) condensing the low boiling fraction of step (b1) to form a        liquid aqueous phase and a liquid organic phase comprising        DCH(s).

The condensing step (b2) may comprise refluxing in a distillationcolumn, such as a fractional distillation column and/or a packeddistillation column.

In one embodiment, additional MAHC(s) and/or ester(s) thereof may beintroduced into condensing step (b2) for reactivedistillation/fractionation for the reasons stated above. Such additionalso increases the amount of liquid available for reflux duringdistillation/fractionation, which increases the efficiency with whichstep (b) separates DCH and water from the other components of themixture (a) provided to step (b).

Step (b) may further comprise:

-   -   (b3) separating the liquid aqueous phase of step (b2) from the        liquid organic phase of step (b2) and    -   (b4) recycling at least some of the liquid aqueous phase of step        (b3) to step (b1) and/or step (b2).

Recycling the liquid aqueous phase to step (b1) may be used tofacilitate recovery of DCH by azeotroping and/or stripping DCH(s) fromthe reaction mixture.

Recycling the liquid aqueous phase to step (b2) may be used to provideadditional liquid for reflux during step (b). When sufficient liquidaqueous phase is recycled to step (b2), the liquid aqueous phase mayflow to the bottom of the distillation/fraction apparatus, so that atleast some of the same liquid aqueous phase is also recycled to step(b1) where it may also facilitate recovery of DCH by azeotroping and/orstripping DCH(s) from the reaction mixture.

The lower boiling fraction produced by step (b) and recovered in step(d) may be subjected to further processing steps. Depending on thefurther processing steps, the lower boiling fraction may be used tosupply DCH(s) for chemical conversion of DCH(s) into other compoundswithout further processing. The lower boiling fraction may be used inprocesses for conversion of DCH(s) into other industrially usefulchemical products.

The lower boiling fraction recovered in step (d) may, for example, besubjected to epoxidation to form epichlorohydrin without additionalpurification of the dichlorohydrin(s) other than via the above-describedoptional liquid-liquid phase separation for recycling an aqueous phasein step (b3). An advantage of the present invention is that the steamintroduced in step (b) not only improves DCH recovery, but also provideswater to the downstream epoxidation process for keeping theconcentration of sodium chloride formed during epoxidation at aconcentration below saturation to avoid undesirable sodium chloridecrystallization during epoxidation.

The above process steps may be carried out independently orsimultaneously with one another. In a preferred embodiment, one or moreof the above process steps is carried out simultaneously with oneanother.

One or more of the above process steps may be carried out continuouslyor discontinuously. One or more of the above process steps arepreferably carried out continuously (i.e., without interruption) for atime period of at least one hour. Preferably, all the above processsteps are carried out continuously for a time period of at least onehour.

At least some of the higher boiling fraction treated in step (b) ispreferably recycled to a hydrochlorination step. In a more preferredembodiment, substantially all the higher boiling fraction treated instep (b) is recycled to a hydrochlorination step. The hydrochlorinationstep is preferably the first step in the hydrochlorination process usedto produce a hydrochlorination effluent containing components of themixture (a).

Recycling the treated higher boiling fraction permits further reactionof MAHC(s) and/or ester(s) thereof and/or MCH(s) and/or ester(s) thereofto form additional DCH, which generally increases the overallhydrochlorination conversion and recovery rates. In that case, theprocess according to the present invention may recover at least 80percent, more preferably at least 90 percent, even more preferably atleast 95 percent, yet more preferably at least 99 percent, and yet evenmore preferably at least 99.9 percent of the DCH(s) produced duringhydrochlorination.

The above process may be conducted using an apparatus according to thepresent invention. The apparatus is now described in more detail inreference to FIG. 1.

FIG. 1 is a block diagram showing the main features of an illustrativeapparatus that may be used and their respective feed streams. Theapparatus comprises at least one reactor (1) and at least one separationdevice (2) comprising at least one liquid-vapor contacting device havinga bottom end and a top end for applying a gradually decreasingtemperature gradient from the bottom end to the top end to substanceswithin the liquid-vapor contacting device.

The at least one reactor (1) may be selected from various knownreactors, such as CSTRs, tubular reactors, and PFRs, and combinationsthereof. When multiple reactors are present, the reactors may beconnected to each other in series or parallel. At least one reactor (1)is connected directly or indirectly to a first feed stream (3)comprising MAHC(s) and a second feed stream (4) comprising chlorinatingagent.

The at least one reactor (1) is connected directly or indirectly to theat least one separation device (2) for conducting at least part of areactor effluent feed stream (5) from the at least one reactor (1) tothe at least one liquid-vapor contacting device of separation device (2)for distillation and/or fractionation. The connection for conducting areactor effluent feed stream (5) from the at least one reactor (1) ispreferably adapted to conduct a liquid-phase feed stream from the atleast one reactor (1).

The at least one separation device (2) comprises a first port (6) forrecovering an effluent stream comprising DCH(s) separated from thereactor effluent feed stream (5) via the at least one distillationand/or fractionation liquid-vapor contacting device of separation device(2) and preferably comprises a first vent (7) for removing gases at thetop of the at least one liquid-vapor contacting device of the separationdevice (2).

The at least one separation device (2) preferably comprises a means forapplying a vacuum to the at least one liquid-vapor contacting device ofthe at least one separation device (2) for reducing the pressure in theat least one liquid-vapor contacting device below ambient atmosphericpressure. The means is preferably a steam-jet ejector.

The at least one liquid-vapor contacting device of the at least oneseparation device (2) is preferably a packed distillation column and/ora distillation column adapted for carrying out fractional distillationunder reflux conditions having a reflux zone for carrying out reflux.

The at least one separation device (2) preferably comprises at least oneflash vessel and the at least one reactor (1) is connected to at leastone liquid-vapor contacting device of the at least one separation device(2) via the at least one flash vessel, whereby the feed stream conductedfrom the reactor (1) is separated into a vapor phase and a liquid phasein the flash vessel by reducing the pressure on the liquid phase and theseparated liquid phase is introduced into the liquid-vapor contactingdevice of separation device (2) for distillation or fractionation.

The at least one separation device (2) also preferably comprises areboiler connected to the at least one liquid-vapor contacting device ofthe at least one separation device (2) for heating the feed stream(s)conducted to the at least one liquid-vapor contacting device of the atleast one separation device (2).

The at least one liquid-vapor contacting device of the separation device(2) is connected directly or indirectly to at least one source ofstripping agent (8) for introducing one or more stripping agents into ahigher boiling fraction. The separation device (2) preferably has asecond port (9) for withdrawing stripped distillation residue feedstream from the separation device (2).

The second port (9) is preferably connected to the at least one reactor(1) via recycle conduit (10) for conducting a recycle feed streamcomprising a stripped distillation residue from the at least oneseparation device (2) to the at least one reactor (1). The recycleconduit (10) preferably has a purge (11) for removal of heavy byproductsfrom the recycle feed stream.

To the extent that components of the above apparatus are exposed tocorrosive materials, such components are preferably fabricated ofmaterials which are resistant to corrosion by the process components.Kirk-Othmer Encyclopedia of Chemical Technology, 2^(nd) Edition (JohnWiley and Sons, 1966), volume 11, pages 323-327, presents an extensivediscussion of the corrosion resistance of metals and non-metals that canbe used in hydrochloric acid and hydrogen chloride service. Specificexamples of suitable materials are disclosed in WO 2006/020234. Specificexamples include metals such as tantalum, suitable metallic alloys(particularly nickel-molybdenum alloys such as Hastalloy C©), orglass-lined equipment.

When milder temperature conditions are used to recover DCH according tothe present invention, less expensive corrosion-resistant materials maybe used in one or more components of the apparatus downstream from thereactor(s), such as distillation or fractionation column(s) (2), thestripping vessel (3) and/or components and conduits linking thosecomponents to each other or to other downstream components. This reducesthe capital investment cost for building a production facility to beamortized, which reduces the overall cost of the process according tothe present invention.

The following examples are for illustrative purposes only and are notintended to limit the scope of the present invention.

Equipment Used in the Examples

Distillation is carried out using a glass distillation column packedwith 6 mm ceramic Intalox saddles, containing two packed bed sections.Feed to the column is located between the two packed bed sections. Thecolumn is provided with a glass reboiler and two partial condensers inseries, also made of glass, for cooling the vapor stream exiting thecolumn. The first condenser is cooled with chilled glycol. A portion ofthe condensate from the first condenser is returned to the column asreflux and the rest of the condensate is collected as product.

Uncondensed vapors from the first condenser are condensed in the secondcondenser operating at a lower temperature and cooled with chilledglycol. The uncondensed vapors exiting the second condenser are passedthrough a set of cold traps before entering the vacuum pump whichprovides vacuum to the whole system. The second condensed liquid-phaseeffluent from the second condenser is collected as product.

Composition and Conditions of Feed Stream Mixture (a)

The feed stream composition and conditions shown in Table 1 below areused to provide the mixture (a) for each example:

TABLE 1 Conditions and Composition Units Feed Rate 2.5 kg/hr FeedTemperature 100 ° C. Feed Pressure 790.8 kPa Feed Composition: Hydrogenchloride 3.7 Weight-percent Water 8.4 Weight-percent1,3-dichloro-2-propanol 38.7 Weight-percent 2,3-dichloro-1-propanol 4.9Weight-percent 3-chloro-1,2-propanediol 9.1 Weight-percent2-chloro-1,3-propanediol 10.8 Weight-percent Esters 5.4 Weight-percentGlycerol 19.0 Weight-percent

As shown in Table 1, the 1,3-dichloro-2-propanol rate is 38.7weight-percent of the 2.5 kg/hr feed rate or 0.97 kg/hr and the2,3-dichloro-1-propanol rate is 4.9 weight-percent of the 2.5 kg/hr feedrate or 0.12 kg/hr. The sum of the 1,3-dichloro-2-propanol feed rate(0.97 kg/hr) and 2,3-dichloro-1-propanol feed rate (0.12 kg/hr), is 1.09kg/hr.

Example 1

In this example, a DCH recovery process is carried out according to thepresent invention using the feed composition and conditions shown inTable 1. The distillation column process conditions used in Example 1are shown in Table 2 below:

TABLE 2 Distillation Column Process Conditions Units Condensertemperature 9.0 ° C. Condenser pressure 6.7 kPa Bottom temperature 130.1° C. Reflux ratio (reflux rate/distillate rate) 0.34 Distillate to feedratio 0.50 Distillate mass vapor fraction 0.25 Pressure drop across thecolumn 1.3 kPa

Steam is fed to the bottom of the distillation column at a pressure of1480 kPa and at a temperature of 197.7° C. at a rate of 1.0 kg/hr.

Using a computer simulation based on actual data obtained with vacuumdistillation conducted with the above equipment and the same feed streamat a column pressure of 1.8 kPa at the same bottom temperature andcondenser temperature, the distillation data shown in Table 3 isobtained.

TABLE 3 Aqueous Organic Subject Vent Overhead Overhead Bottoms UnitsRate 0.17 0.18 1.41 1.17 kg/hr HCl 0.08 12.63 4.85 0.03 wt. % H₂O 86.8883.82 23.15 0.61 wt. % 1,3-dichloro-2-propanol 12.33 3.29 64.35 3.11 wt.% 2,3-dichloro-1-propanol 0.71 0.25 7.63 1.23 wt. %3-chloro-1,2-propanediol — — 0.01 19.42 wt. % 2-chloro-1,3-propanediol —— 0.01 23.20 wt. % glycerin — — — 40.83 wt. %

“Vent” refers to stream 7 in FIG. 1. “Aqueous Overhead” refers to theaqueous phase of a two-phase liquid-liquid decanter used to separateoverhead stream 6 of FIG. 1 after condensation. “Organic Overhead”refers to the organic phase of a two-phase liquid-liquid decanter usedto separate overhead stream 6 of FIG. 1 after condensation. “Bottoms”refers to the distillation residue stream 9 of FIG. 1. Hyphen (“-”)indicates that the weight-percent value was below 0.01.

The rate at which DCH is recovered in the overhead via distillation step(b) may be calculated as the difference between the DCH feed rate (1.09kg/hr as shown in the explanation for Table 1) and the DCH bottom rate(0.05 kg/hr) or 1.04 kg/hr.

DCH recovery is therefore 95.4 percent (1.04÷1.09×100).

Comparative Example

In this comparative example, DCH recovery is determined based on thesame distillation process equipment, conditions and feed stream as inExample 1, except that distillation was carried out without steaminjection.

The data obtained is shown below in Table 4.

TABLE 4 Aqueous Organic Subject Vent Overhead Overhead Bottoms UnitsRate 0.03 0.18 0.88 1.42 kg/hr HCl 68.18 29.35 2.08 — wt. % H₂O 20.5668.68 9.37 0.01 wt. % 1,3-dichloro-2-propanol 10.86 1.87 81.83 17.17 wt.% 2,3-dichloro-1-propanol 0.40 0.10 6.69 4.51 wt. %3-chloro-1,2-propanediol — — 0.01 16.01 wt. % 2-chloro-1,3-propanediol —— 0.01 19.11 wt. % glycerin — — — 33.64 wt. %

The DCH overhead rate may be calculated as 0.782 kg/hr (1.09 kg/hr DCHfeed rate minus 0.308 kg/hr DCH bottom rate). DCH recovery is calculatedto be 71.1 percent (0.782 kg/hr÷1.09 kg/hr×100).

As can be seen from the foregoing, Example 1 according to the presentinvention is capable of obtaining a greater DCH recovery than theComparative Example carried out under substantially the same conditionsother than steam injection.

Advantages of the present invention include:

-   -   1. A wider selection of vacuum devices and the ability to use of        a more economical steam-jet ejector, thereby reducing capital        and operating costs;    -   2. Reduction of column size for a given feed volume due to the        ability to operate at higher pressures, further reducing capital        investment required;    -   3. Reduced heavy byproducts formation due to reduced        distillation bottoms temperatures for increased product yield        and reduced energy requirements for byproduct disposal;    -   4. Additional water introduced by steam stripping facilitates        any downstream epoxidation process by keeping the concentration        of sodium chloride formed during epoxidation below the        saturation level.

What is claimed is:
 1. A process for recovering dichlorohydrin(s) from amixture comprising dichlorohydrin(s), one or more compounds selectedfrom ester(s) of chlorohydrin(s), monochlorohydrin(s), andmultihydroxylated-aliphatic hydrocarbon compound(s); water; andoptionally one or more substances selected from chlorinating agent(s),catalyst(s), ester(s) of catalyst(s), and heavy byproduct(s), whereinthe process comprises: (a) providing a vapor or liquid phase mixturecomprising dichlorohydrin(s), one or more compounds selected fromester(s) of chlorohydrin(s), monochlorohydrin(s), andmultihydroxylated-aliphatic hydrocarbon compound(s) and ester(s)thereof; water, wherein the water present in the mixture is the waterproduced in a hydrochlorination reaction; and optionally one or moresubstances selected from chlorinating agent(s), catalyst(s), ester(s) ofcatalyst(s), and heavy byproduct(s); (b) distilling or fractionating themixture of step (a) in one or more unit operations to separate a lowerboiling fraction comprising dichlorohydrin(s) and other lower boilingcomponents from the mixture of step (a), to form a higher boilingfraction comprising the residue of the distillation or fractionation;and simultaneously introducing at least one stripping agent into contactwith the higher boiling fraction; wherein the at least one strippingagent is an azeotroping agent for the dichlorohydrin(s); and wherein theat least one stripping agent contacts the higher boiling fraction andstrips dichlorohydrin(s) from the higher boiling fraction into a vaporphase: (1) to produce a lower boiling fraction enriched withdichlorohydrin(s) and the at least one stripping agent; and (2) to lowerthe boiling temperature of the higher boiling fraction to minimize theformation of heavy byproducts; and (c) recovering at least a portion ofthe lower boiling fraction produced in step (b).
 2. The processaccording to claim 1, wherein step (h) is carried out at a pressure inthe range from 1 kPa to 0.12 MPa; and wherein the temperature of thehigher boiling fraction during step (b) is in the range from 50° C. to139° C.
 3. The process according to claim 1, wherein the stripping agentcomprises steam.
 4. The process according to claim wherein at least onemonochlorohydrin or ester thereof is present in the mixture provided instep (a) and in the high-boiling fraction of step (b); or wherein atleast one multihydroxylated-aliphatic hydrocarbon compound is present inthe mixture provided in step (a) and in the high-boiling fraction ofstep (b).
 5. The process according to claim 1, (1) wherein the mixtureprovided in step (a) further comprises a catalyst for hydrochlorinatingmonochlorohydrin(s) and/or ester(s) thereof and/ormultihydroxylated-aliphatic hydrocarbon compound(s) and/or ester(s)thereof; and wherein the catalyst is at least one carboxylic acid, atleast one ester of at least one carboxylic acid, or a combinationthereof, having a boiling point during step (b) greater than the boilingpoint of the highest boiling dichlorohydrin during step (b); or (2)wherein the catalyst (i) is a carboxylate derivative having from two toabout 20 carbon atoms and containing at least one functional groupselected from the group comprising an amine, an alcohol, a halogen, asulfhydryl, an ether, an ester, or a combination thereof, wherein thefunctional group is attached no closer to the acid function than thealpha carbon; or a precursor thereto; (ii) is less volatile than thedichlorohydrin; and (iii) contains heteroatom substituents.
 6. Theprocess according to claim 1, wherein the mixture provided in step (a)further comprises water; and wherein step (b) comprises: (b1) vaporizingan azeotropic mixture of dichlorohydrin(s) and water from the mixture ofstep (a) to separate a lower boiling fraction comprising at leastdichlorohydrin(s) and water from the mixture of step (a); and (b2)condensing the lower boiling fraction of step (b1) to form a liquidaqueous phase and a liquid organic phase comprising dichlorohydrin(s);(b3) introducing at least one multi-hydroxylated aliphatic hydrocarboncompound and/or ester thereof into the condensing step (b2); (b4)separating the liquid aqueous phase of step (b2) from the liquid organicphase of step (b2); and (b5) recycling the liquid aqueous phase of step(b3) to step (b1) and/or step (b2).
 7. The process according to claim 1,wherein the mixture provided in step (a) further comprises heavybyproducts; and wherein the amount of heavy byproducts in the higherboiling fraction of step (b) does not exceed 110 percent of the amountof heavy byproducts in the mixture provided in step (a).
 8. The processaccording to claim 1, wherein dichlorohydrin(s) is/are recovered fromthe lower boiling fraction of step (b).
 9. The process according toclaim 1, including further the step of epoxidizing the lower boilingfraction recovered in step (b) to form epichlorohydrin withoutadditional purification of the dichlorohydrin(s).
 10. The processaccording to claim 1, (i) wherein all of the steps of the process arecarried out simultaneously with each other and the process is carriedout continuously for a predetermined period of time; or (ii) wherein atleast a portion of the higher boiling fraction of step (b) is recycledto the hydrochlorination step; or (iii) wherein at least 95 percent ofthe dichlorohydrin(s) produced during hydrochlorination is recovered instep (b).